Devices exist to measure and record eye movements. While many variations exist, eye tracking devices often include a camera attached to a computer which focuses on one or both of an individual's eyes and records eye movement. Some of such devices use contrast to locate the center of the pupil and use infrared illumination to create one or more corneal reflections, and relating the position of these points to determine a fixation point of the eye.
Eye movement data is typically categorized as fixations, smooth pursuit movements, saccades, or blinks. A fixation is said to occur when the eye gaze pauses in a certain position while a saccade is when one's gaze is moving to another position. By measuring and recording these movements, eye tracking devices may be used to determine where on a two-dimensional plane or image a viewer is looking and for how long. Further, the path one's eyes followed over the image may also be determined.
Eye tracking devices have many applications including, for example, advertising and market research. As disclosed in U.S. Pat. No. 6,712,468, eye tracking devices have been used to track the eyes of a person viewing a webpage. Representations may then be generated to show, e.g., designers of the webpage which regions of the webpage were viewed and which regions were not.